Thermo-developable diazo coatings employing dicyandiamide compositions



The present invention relates to a light sensitive, heatdevelopable diazonium composition and elements including such compositions. More specifically, this invention relates to diazonium compositions and products which may be developed by heat without the application of any discrete developing material.

The diazo compositions most widely employed in conventional diazo coatings comprise a light decomposable diazonium salt, an organic coupling component and an acid. An element coated with this type of composition is exposed to light through a negative or positive and the diazonium salt is decomposed only in those areas exposed to the light. The unexposed areas remain undecomposed and are subject to further reaction in the presence of an alkaline reagent to produce a colored image with the coupler, whereas the exposed areas potential for being developed have been destroyed. The color producing reaction is produced by an alkaline compound, generally ammonia, either as a gas or in a solution.

The prior art heat developable diazo types also have relatively poor shelf life under high humidity and temperature conditions.

An object of this invention is to provide a light sensitive diazonium composition that is developable by heat.

Another object of this invention is to provide for a diazo composition which may be employed in relatively simple azo copying devices where no means for generating developing fluids or evacuating noxious by-product vapors need be provided.

Another object of this invention is the provision of a diazonium composition which may be employed as coatings on various substrates to produce highly useful photosensitive copying means.

Another object of this invention is to provide heat developable diazo papers that have improved shelf life.

In conventional diazonium color forming systems, the alkaline reagent does not enter into the coupling reaction. Its function is to neutralize the acid present and change the environment from acidic to neutral or basic. The coupling mechanism then takes place in the neutral or basic environment and the desired color formation takes place.

Commonly used developing techniques are somewhat cumbersome in that they use a two-step process of exposure followed by development with a separate alkaline medium. To obviate the requirement of a separate developing medium, diazo compositions have been devised which contain compounds capable of yielding alkaline developing products when decomposed by heat. Stated otherwise, the present invention comprises the in situ formation of an alkaline developing product which avoids the use of a separate alkaline treating step.

It has been found that dicyandiamide and analogous compounds or dicyandiamide and analogous compounds condensed with aldehydes will decompose when exposed to heat in the presence of an acid to yield alkaline decomposition products. The dicyandiamide or analogous compounds are combined with a diazo salt, coupler, acid, and stabilizer in one coating composition and applied to a substrate to produce a photosensitive heat developable coating.

The prior art discloses the use of resin or semi-resinous condensation product of dicyandiamide and formaldehyde in diazo-type layers to improve their stability to decomposition on storage and improve fastness to washing of the image. However, such systems do not rely upon the dicyandiamide compounds for the situ formation of basic decomposition products upon heating, thus avoiding the need for a separate alkaline treatment for developing the diazo composition.

Other compositions used in heat developable diazo coatings comprising the reaction product of hydroxyl amine and phloroglucinol i.e. triketohexamethylenetrioxime. This compound decomposes when heated to yield phloroglucinol triketohexamethylene and ammonium hydroxide.

When triketohexamethylenetrioxime is added to a light sensitive diazo composition containing a heat decomposable acid or the salt of a strong base and a volatile weak acid, a coupler and alkaline compound are generated when the coating is heated and the acid or acid salt is expelled. The alkaline compound formed in situ will neutralize or make the compound slightly alkaline and at raised temperature induces a rapid coupling.

The diazonium system of the present invention is much less complex in that a heat decomposable acid or strong salt of a weak acid need not be employed. The alkaline environment generated by the heat decomposition of dicyandiamide compounds is sufficient to promote the coupling reaction in the presence of acids less volatile and more stable to heat than those contemplated in prior techniques. Moreover, the thermal decomposition products of dicyandiamide or its derivatives do not act as couplers in the present system, whereas the decomposition of triketohexamethylenetrioxime, according to the prior art, does produce a coupler.

Thus, the present invention relates to heat developable, light sensitive diazonium compositions comprising light sensitive diazonium salts, diazonium couplers, an acid and a dicyandiamide composition which decomposes when heated to furnish alkaline decomposition products. The alkaline products reduce the acidity of the system and enable the diazonium salt and coupler to undergo a color forming reaction.

In the present description and the following claims, the expression dicyandiamide composition is intended to include dicyandiamide, its derivatives and mixtures thereof which decompose into alkaline products under the influence of heat.

Although dicyandiamide is a correct chemical term, the use of cyanoguanidine gives a better description of the compound. Both terms designate the same material and can be used interchangeably.

Dicyandiamide, in the absence of citric or malonic acid, does not form a coupler. Its only purpose is to neutralize the acid upon thermal reaction. In the absence of an acid, slow decomposition of dicyandiamide starts at C. or above. Decomposition becomes rapid only above the melting point 206 C. The preferred embodiment of this invention incorporates an acid with the dicyandiamide composition although it is Within the scope of this disclosure to omit the acidic material should higher developing temperatures present no problem.

Applicant does not wish to be limited by any theory as to the nature of the invention. However, it appears that the reaction mechanism involves the transformation of the neutral cyanoguanidine to guanyl urea and guanidine derivatives of an alkaline nature under the effect of H+ ions and heat. Should citric acid also be present in the formulation, along with a coupler, two different dyes are being formed:

(a) A regular diazo-coupler reaction dye.

(b) A dye described by S.N. 163,055 filed on December 29, 1961.

It should also be noted that shelf life is better than previously described formulations employing urea as a base generator. The urea compounds last for one Week, Whereas under the same conditions, the formulations described and disclosed by this invention last for 2-3 weeks, which is a substantial improvement over the prior art. Furthermore, the compositions of this invention can be differentiated by the different compounds employed.

The following examples are illustrative of this invention but are not intended in any way to limit the scope.

The following compositions are coated on paper.

ents are also operable and within the broad scope of this invention:

When a system employing the diazonium composition of this reaction is applied by a process employing two or more coatings, the ingredients comprising dicyandiamide will be referred to as dicyandiamide compositions which Example Diazonium Salt Number Gin. Acid Gm. Dieyandiamide Composition Gm.

p-Diazo methyl-hydroxy ethyl aniline zinc chloride 1 Tartarie... 2 Dieyandiamide 5 2,5,1 1dilgglltoxy-i morpholino benzene diazonium chloride A zine 1 d 2 .d0

e l on e. p-Diazo methyl-hydroxy ethyl aniline zinc chloride 1 Maleie 5 Dicyandiamide formaldehyde... d0 1 Tartaric 2 d p-Diazo-N diethyl-l'l-phenetidine zinc chloride 1 do.. 2 p-Diazo-l morpholino benzene lg zinc chloride Citric. 5 Dodeeyldicyandiamidc Example Color at Number Diazo Coupler Gm. Diazo Stabilizer Gm. Solvent Ml. l-l75 C. for

30-60 sec.

Phloroglucinol 2 Nil BrownJBlack. do 2 Nil D0. Sodium salt of 2, 3, dihydroxy 2 1, 3, 6 trisodium naphthalene sulfonate Purple.

naphthalene ti sulfonic acid. do 2 d0 1 Do. do 2 Nil 1: 1 methanolzwatern 100 Deep Blue.

2, 3, dihydroxy naphthalene 2 1, 3, 6 trisodium naphthalene sull'onat 2 Methanol. 100 D0.

No'rn.-1he above components of the above examples can be mixed together and applied to paper or a suitable substrate or each component can be applied individually or in any combination with the other components to one, or both, or any combination of sides to a porous 0r nonporous substrate The dicyandiamide condensation of product is prepared by heating equimolecular amounts of dicy-andiamide and formaldehyde solution (37% by Weight) under reflux conditions between and C. for 30 minutes. For example, 42 grams of cyanoguanidine and 40.4 grams of formaldehyde solution (37%) are heated for 30 minutes at 95 to 100 C. under reflux. The condensate solution is either used as a separate coating or as a solvent for the acid, diazo and coupler. The low molecular weight condensation products are soluble in water. Upon standing, a white precipitate of higher molecular weight material develops which can be redissolved upon heating. Molecular weights of the condensates have not been precisely determined. However, generally speaking, they are water soluble at ambient temperatures. Variations of heating time (up to one hour or more) or ratios of the initial materials change the reaction products somewhat. Addition of an alkaline catalyst (KOH) increases the rate of reaction, thus causing the formation of higher molecular weight condensation products.

The following variation on the above formulas is also within the broad scope of the invention and is one of the preferred embodiments thereof:

p-Diazo-2,5-diethoxy-l-morpholino-benzene /2 zinc chloride gr 4.0 Sodium-2,3-dihydroxynaphthalene-6-sulfonate gr 1.4 Citric acid gr 10 Thiourea gr 5 Cyanoguanidine gr 5 Water ml 100 by definition include the dicyandiamide compositions listed in the examples, cyclohexyl dicyandiamide, o-tolyl dicyandiamide, p-tolyl dicyandiamide as well as aldehyde condensation products thereof with formaldehyde, acetaldehyde, paraformaldehyde and benzaldehyde and optionally a film forming material, any chemical or physical mixture thereof and any combination thereof including individual components recited above.

The other coating or coatings will be referred to as a diazo composition, Which will by definition include a diazonium salt, acid and couplers as given by the examples and specification and equivalents thereof and optionally a resinous film forming material, solvents and stabilizers given by the examples, specification and equivalents thereof, any physical or chemical mixture thereof and any combination thereof including individual components recited above.

The application of the ingredients of the dicyandiamide composition, individually or any combination thereof, and the ingredients of the diazo composition individually or any combination thereof to either both or one side or any combination thereof of a substrate will be defined as a substrate contiguous to the diazo composition and dicyandiamide composition or a process of applying a diazo composition and dicyandiamide composition contiguous to a substrate. This contiguous relation is also one where the compositions will be on the substrate where the viscosity of the compositions are high or the substrate is non-porous or both, and in the substrate where the viscosity of the compositions are low and the substrate is porous or both.

Various combinations of the diazo composition and the dicyanadiamide composition will be considered contiguous with the substrate for purposes of definition, such as a separate dicyandiamide composition formed as a first layer over which the diazo composition is separately coated. The diazo composition can be the first coating and the dicyandiamide composition can be used as the second coating. Alternate layers of a dicyandiamide composition and diazo composition or diazo compositions can be used such as three coatings of different or the same diazo compositions. One, two, three and more than three diazo compositions can be used to produce different effects. Several layers of the diazo compositions can be used with one coating of a dicyandiamide composition on the bottom or top layer of the diazo compositions. When a porous or permeable substrate is used, a coating of dicyandiamide composition on the reverse side of the substrate containing the diazo composition can be used.

The above combinations are given as non-limiting examples of the various combinations of diazo compositions and dicyandiamide compositions, other combinations obvious to one skilled in the art are too numerous to mention but are also contemplated.

The dicyandiamide compositions of this invention include not only those listed in the examples but also cyclohexyl dicyandiamide, o-tolyl dicyandiamide, p-tolyl dicyandiamide, as well as aldehyde condensation products of these dicyandiamides such as for example formaldehyde, acetaldehyde, paraformaldehyde, benzaldehyde condensation products, as well as other cyanoguanidines and aldehydes known to those skilled in the art. The above reactants, however, are illustrative and not to be taken as limiting the disclosure. Any chemical or physical combination of the above are also to be considered dicyandiamide compositions.

Non-limiting examples of diazonium salts in addition to those given in the examples include:

p-diazo-dimethyl aniline zinc chloride p-diazo-diethyl aniline zinc chloride p-diazo-ethyl-hydroxyethyl aniline /2 zinc chloride p-diazo-Z,5-diethoxy-benzoylaniline /a zinc chloride p-diazo-ethyl-benzylaniline /2 zinc chloride p-diazo-l-morpholinobenzene /2 zinc chloride p-diazo-2,5-dibutoxy-l-morpholinobenzene /2 zinc chloride p-diazo-2,5-diethoxy-l-morpholinobenzene zinc chloride p-diazo-N-ethyl-O-toluidine zinc chloride, etc.

Any combination of the above are to be considered diazonium salts within the scope of this invention.

Non-limiting examples of the diazo couplers include those given in the examples as well as:

2,S-dihydroxy-naphthalene or its 6 sulfonic acid derivative 2,7-dihydroxy-naphthalene 1,7-aminonaphthol, 2-hydroxy-8-biguanidine phloroglucinol acetoacetanilide resorcinol and its derivatives Any combination of the above are considered to be diazo couplers within the scope of this invention.

Non-limiting examples of the diazo stabilizer include those given in the examples as well as:

1,3,6-naphthalene-trisulfonic acid, sodium salt allylthiourea hydroxy allylthiourea Any combination of the above are considered to be diazo stabilizers within the scope of this invention.

Non-limiting examples of acids within the scope of this invention include those given in the examples as well as:

maleic glyoxilic tartaric sulfanilic boric citric Any combination of the above are considered to be acids within the scope of this invention.

The film forming resinous material referred to in the specification and claims of this application include cellulose nitrate, cellulose acetate, cellulose acetate butyrate,

as well as other cellulose ester or ethers, polyvinyl alcohol, polyvinyl acetate, polyvinyl pyrrolidene in solution or emulsion form, and any combination of the above including mixtures and copolymers.

The following porous or non-porous substrates are also within the broad scope of this invention:

glass fiber, glass, metal plastic film such as cellulose acetate, propionate, acetate butyrate polyethylene terephthalate (Mylar) paper, wood, composition board, etc.

It should also be clear that many combinations of various dicyandiamide compositions and diazo compositions are evident from the above equivalents and examples and that these combinations, although not specifically delineated, are also within the broad scope of this invention.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. A light-sensitive heat-developable diazonium composition comprising a light-sensitive diazonium salt, a diazo coupler, a diazonium stabilizing acid and a dicyandiamide composition selected from at least one member of the group consisting of dicyandiamide, dodecyldicyandiamide, cyclohexyldicyandiamide, o-tolyldicyandiamide, p-tolyldicyandiamide, dicyandiamide formaldehyde, dicyandiamide acetaldehyde, dicyandiamide paraformaldehyde, and dicyandiamide benzaldehyde.

2. A light-sensitive heat-developable diazonium composition comprising 0.5% to 10% by weight of a diazonium salt, from 1% to 10% by weight of a diazo coupler, from 1% to 20% by weight of a diazonium stabilizing acid, and from 3% to 25% by weight of a dicyandiamide composition selected from at least one member of the group consisting of dicyandiamide, dodecyldicyandiamide, cyclohexyldicyandiamide, o-tolyldicyandiamide, p-tolyldicyandiamide, dicyandiamide formaldehyde, dicyandiamide acetyldehyde, dicyandiamide paraformaldehyde, and dicyandiamide benzaldehyde.

3. A light-sensitive heat-developable element comprising a substrate coated with a light-sensitive diazonium salt, a diazonium stabilizing acid, a diazonium coupler, a filmforming material, and a dicyandiamide composition selected from at least one member of the group consisting of dicyandiamide, dodecyldicyandiamide, cyclohexyldicyandiamide, o-tolyldicyandiamide, p-tolyldicyandiamide, dicyandiamide formaldehyde, dicyandiamide acetaldehyde, dicyandiamide paraformaldehyde, dicyandiamide benzalidehyde.

4. A light-sensitive heat-developable element comprising a heat stable substrate, a dicyandiamide coating on said substrate selected from at least one member of the group consisting of dicyandiamide, dodecyldicyandiamide, cyclohexyldicyandiamide, o-tolyldicyan-diamide, p-tolyldicyandiamide, dicyandiamide formaldehyde, dicyandiamide acetaldehyde, dicyandiamide paraformaldehyde and dicyandiamide benzaldehyde, and a second discrete coating on such substrate contiguous with the first coating comprising a light-sensitive diazonium salt, a diazonium coupler and a diazonium stabilizing acid.

5. A light-sensitive heat-developable element comprising a heat stable substrate, one coating on said substrate comprising from 3 to 25% by weight of a dicyandiamide composition selected from at least one member of the group consisting of dicyandiamide, dodecyldicyandiamide, cyclohexyldicyandiamide, o-tolyldicyandiamide, p-tolyldicyandiamide, dicyandiamide formaldehyde, dicyandiamide acetaldehyde, dicyandiamide paraformaldehyde and dicyandiamide benzaldehyde, and a second discrete coating on said substrate contiguous with said first coating com- 7 prising a light-sensitive diazonium salt, a diazon-iurn icoupler and a diazonium stabilizing acid.

6. A light-sensitive heat-developable element impregnated with from 3% to 25% by weight of a dicyandiamide composition selected from at least one member of the group consisting of dicyandiamide, dodecyldicyandiamide, cyclohexyldicyandiamide, o-tolyldicyandiamide, p-tolyldicyandiamide, dicyandiamide formaldehyde, dicyandiamide acetaldehyde, dicyandiamide paraformaldehyde and dicyandiamide benzaldehyde, and a coating on said substrate comprising a light-sensitive diazonium salt, a diazoniurn coupler and a diazonium stabilizing acid.

7. A light-sensitive heat-developable diazotype composition comprising an aqueous solution of a light-sensitive diazonium compound, an azo dye coupler and dicyandi- 1 amide, said solution being stabilized at an acidic pH.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS 11/1960 France.

7/1959 Great Britain.

NORMAN G. TORCHIN, Primary Examiner.

R. L. STONE, A. D. RICCI, Assistant Examiners. 

1. A LIGHT-SENSITIVE HEAT-DEVELOPABLE DIAZONIUM COMPO SITION COMPRISING A LIGHT-SENSITIVE DIAZONIUM SALT, A DIAZO COUPLER, A DIAZONIUM STABILIZING ACID AND A DICYANDIAMIDE COMPOSITION SELECTED FROM AT LEAST ONE MEMBER OF THE GROUP CONSISTING OF DICYANDIAMIDE, DODECYLDICYANDIAMIDE, CYCLOHEXYLDICYANDIAMIDE, O-TOLYLDICYANDIAMIDE, P-TOLY DICYANDIAMIDE, DICYANDIAMINDE FORMALDEHYDE, DICYANDIAMIDE ACETALDEHYDE, DICYANDIAMIDE PARAFORMALDEHYDE, AND DICYANDIAMIDE BENZALDEHDYE. 